Static pressure is one of the terms that sometimes comes up when installing new heating, ventilation, and air conditioning (HVAC) system or making repairs to an old one. You could go decades as a homeowner without ever encountering static pressure or you might find yourself suffering from its consequences. What is static pressure? Let’s take a look.

About Static Pressure

The resistance to the flow of air in your ductwork is referred to as static pressure. You could think of it as the result of factors that limit the flow of air through your ductwork as it travels to the rooms in your home. The static pressure in your HVAC system can cause problems if it is too low or too high. It is not possible to deliver air with no resistance; however, it is best to keep the pressure balanced. The issues that can arise from too high or low static pressure include a shortening of your system’s lifespan and static pressure problems may also cause it to use more energy than it should.

A simple way to illustrate static pressure is to imagine a garden hose. There is a difference between how water flows from the hose if the opening is unblocked and if you partially block it with your thumb. The wider the opening, the lower the pressure, the smaller the opening the higher the pressure. Your blood pressure is another good analogy where the tighter the space, the higher the pressure. Within your home’s ductwork, there is a similar dynamic. The tighter your ductwork, the greater the velocity of the air within. If it has been determined that your static pressure is low, you will want to reduce the duct size for greater static pressure. You would increase the duct size if you need to lower the pressure.

If the static pressure in your system is wrong, it can make the equipment work harder or even shut the system down. Static pressure impacts how well your system runs and how high your utility bills get.

Ways that Static Pressure Affects Your HVAC System

If your static pressure is too high or low, you might see these signs:

Noisy Operation

Your blower motor might be noisier than it is at other times because it is working harder. The motor might sound like a jet engine as it takes off or it might be just a little too loud. The noise may get even louder as your HVAC system heats up.

Inconsistent Heating or Cooling

In systems with high static pressure, you may notice that only one part of a room is receiving airflow. The result can be hot and cold areas that make it hard to find a comfortable place no matter where you are.

Longer Running

If your HVAC system is not generating sufficient airflow, it won’t efficiently cool or heat your home. The result is that the system will have to work for longer to get your home to the right temperature. Another thing that your HVAC system does when it is working properly is it dries out the air in your home in warm weather. A system with low airflow won’t effectively dry out all parts of a home so you may notice that there are humid or overly warm spots.

Higher Cost

The increased workload for your system means that it will use more energy and cost more to operate. If the ducts are not sealed, they will leak even more if the static pressure is high and cause an even greater spike in your utility costs. If you see high energy bills without an obvious indication of the cause, the problem might be static pressure.

Broken Parts

Static pressure can also cost you more in terms of repairs. One of the side effects of a system that runs for longer is that the parts become damaged more quickly. For example, your heat exchanger may crack prematurely if the system is unable to dissipate the heat it is generating quickly enough. Overall, high static pressure will result in a shorter lifespan for your HVAC system as a whole.

Ways to Fix Static Pressure

Static pressure problems originate in one of two areas: inadequate supply side ductwork or inadequate return to the furnace. You can solve static pressure difficulties with these steps:

Clean Your Coils

The coils heat or cool air passing through them and can gather dust. If coils are dirty, the air won’t move as it should and you may see static pressure increase. If the return is too small, the dirty coils will just make things worse.

Increase Static Pressure if you Add to Your Square Footage

If you build an addition to your home, you are going to have to add another duct run. With the static pressure as it presently is, that other duct run will lower the air that goes to other rooms. You can correct this by increasing the static pressure.

Don’t Use Too-Restrictive Filters

A filter with an overly high Minimum Efficiency Reporting Values (MERV) rating that does not allow an adequate airflow through can create static pressure issues for your system. It may also affect air quality in the home since not as much air will reach your rooms. A restrictive filter will cause your system to work harder to pull the air through, which means that it will use more electricity and be more expensive to run. It is recommended that you use less-expensive low-MERV filters and change them more often to prevent high static pressure problems.

Replace Dirty Filters

If your filters are dirty, they will become restrictive similar to the high-MERV ones above. Because it is dirty, the system will have to work harder than it should just as if you were using a restrictive air filter. The dirt from the filter may also cause air quality problems in your home.

Correctly Size and Design Your Ductwork

If your ducts are too small, the static pressure will be high and your furnace may not get enough air. Oversized ductwork creates the opposite problem with low static pressure. The problem can also come from too much bending and dipping in the ductwork, which can also increase resistance in the same way that a bend in your garden hose affects the water pressure.

Correctly Size Your Equipment

A furnace that is too big is going to create high static pressure within the home’s ductwork. An undersized furnace will cause low static pressure and won’t be able to deliver enough warm air to keep the home comfortable.

Ways to Prevent Static Pressure Problems

To prevent static pressure issues, work with an HVAC company that knows how to evaluate your whole system. Your HVAC contractor should check all of the components in your home including your air conditioner, furnace, and ductwork. To regulate static pressure, it’s necessary to calculate what the correct pressure should be. Your HVAC technician will measure the static pressure in at least two locations to find the source of the resistance. They will also do a load calculation to determine whether your ductwork is correctly-sized. They should also be able to measure airflow. Other steps to avoid static pressure problems include ductwork maintenance steps like:

Regular air filter replacement

  • Checking ductwork for leaks in the form of holes.
  • Keep vents clear by cleaning them regularly and not obstructing them with furniture.
  • Maintain HVAC components according to a regular schedule.

Altering Ductwork to Fix Static Pressure Problems

The most reliable way to correct static pressure trouble is to redesign your ductwork. The solution often involves simple, inexpensive adjustments where only small changes are needed. A minor increase or decrease in size may be all you need to increase or decrease static pressure and improve airflow.

Ductwork is Key to the Function of Your HVAC System

If your ductwork is no good, your HVAC system won’t heat and cool your home as it should even if the other components are in great shape. Poor ductwork directly impacts your home’s comfort level and can even affect your health. Pollutants can enter your indoor air if your ductwork is not properly fitted to your HVAC system. On the other hand, professionally installed ductwork will ensure that the temperatures in all rooms of your home stay consistent. Your HVAC system will deliver clean air to every room and the static pressure in your ducts will ensure that your air filters work as they should.

Static pressure problems may seem difficult ones to manage but not for us at Delaware Heat and Air. If you are dealing with the issues we have described above, contact us to set up an appointment. Our technicians can get your HVAC system working properly and return your home to a comfortable temperature.